Conventionally, a magnetic disk to be loaded onto a magnetic disk device such as a hard disk drive (HDD) has a protecting layer and a lubricating layer provided on a magnetic recording layer formed on a substrate in order to maintain a durability and a reliability of the magnetic disk. In particular, the lubricating layer to be used on an uppermost surface is demanded to have various properties such as a long-term stability, a chemical material resistance, a frictional property and a heat resisting property.
For the demand, conventionally, a perfluoropolyether based lubricant has often been used as a lubricant for the magnetic disk. For example, as disclosed in JP-A-62-66417 (Patent Document 1), there has been known a magnetic recording medium to which a perfluoroalkylpolyether based lubricant having a structure of HOCH2—CF2O—(C2F4O)p-(CF2O)q-CH2OH is applied.
As a commercial product of the perfluoropolyether based lubricant, there is often used a FOMBLIN Z based lubricant manufactured by Solvay Solexis Co., Ltd., which has a high heat resistance and a long-term stability. In order to remove an impurity from the commercial product of the lubricant or to properly distribute a molecular weight of the lubricant because the lubricant is a polymeric material, various purifications have been made and the lubricant has been used for the magnetic disk.
Patent Document 1: JP-A-62-66417